Process of making ammonium sulfate and sulfur from gas.



W. FELD. PROCESS OF MAKING AMMONIUM SULFATE AND SULFUR FROM GAS.APPLIOATION FILED MAR. 29, 1911.

1,011,0'. v "Patented Dc.5,191 1.

IN l/EATHW jy w I WELT/YEW Pam WALTHEB FELD, F LINZ, GERMANY.

PROCESS OF MAKING AMMONIUM SULFATE AND SULFUR FROM GAS.

To all whom it ma/y concern:

Be it known that I, WALTHER FELD, a subject of the King of Prussia andthe (Jerman Emperor, of Linz-on-the-Rhine, in the German Empire, haveinvented new and useful improvements in effecting the combination, withsulfurous acid, of ammonia or'of amrmonia and sulfureted hydrogencontained in gases, vapors, or liquids and the obtainment of ammoniumsulfate, of which the follow-' ing is a specification.

The combination of ammonia and sulfureted hydrogen, contained in gases,vapors, or liquids, by treating the gases, va-

pors, or liquids with sulfurous acid in the gaseous form, or with freesulfurous acid, or with bisulfites dissolved in water, is known, theaction of the sulfurous acid on the ammonia producing ammonium sulfite,while the action of sulfurous acid on sulfureted hydrogen liberatessulfur. This process has the disadvantage that, in consequence of thedissociation of the ammonium sulfite and of the high vapor tension ofsulfurous acid,

and of ammonia, a part of the sulfurous acid and part of the ammonia areleft uncombined. For these same reasons sulfurous acid contained ingases cannot be retained by washing them with ammonia water and theevaporation of solutions containing ammonia sulfite is attended withreat losses. Furthermore, the ammonia-sul te crystals obtainedby thisknown process, will constantly lose ammonia and sulfurous acid 335, andthese crystals, on account of their reducing properties, are notsuitable for use as a manure. It has been proposed to oxidize theammonium sulfite into sulfate by treatment with air, but by suchtreatment ammonia and sulfurous acid-are evaporated and lost with theescaping air, and the oxidation is not complete. It has also beenproposed to convert the am onium sulfite into ammonium sulfate, bytreatment with sulfuric acid, but this is not practicable as it is theintention of my invention to produce sulfate of ammonia by usingthe'sulfur contained in raw gases, or vapors, or raw liquors, withoutusing sulfuric acid. The

aforesaid inconveniences are especially apparent when the gases, vaporsor liquids, containing the ammonia, contain no sulfureted hydrogen, "orless than one proportion, by weight, or sulfureted hydrogen toSpecification of Letters Patent.

Application filed March 29, 1911. serial No. 817,678.

monia and free sulfur.

Patented Dec. 5, 1911.

one proportion, by weight, of ammonia. I have found that, in order toovercome these disadvantages, it is necessary to avoid the finalformation of ammonium sulfitc and to control the reaction of the gases,for instance ammonia, or sulfureted hydrogen, or both, with sulfurousacid, in such a way that only thiosulfates, or polythionates, or both,(which I will hereinafter refer -to generally as thionates are produced.For this purpose it is necessary to carry out the reactions betweenammonia and sulfureted hydrogen or either, and sulfurous acid in thepresence of such an excess of free'sulfur (or a sulfur yieldingsubstance, such as a thionate, a sulfid or polysulfid' of an alkali, oran earth-alkali, or ammonia) that only thiosulfate of polythionate willbe formed. With gases, vapors, or liquids, which contain more sulfuretedhydrogen than is equivalent to the ammonia, it is-for instance necessaryto supply so much sulfurous acid that, in spite of the slow reactionbetween sulfurous acid and sulfureted hydrogen, for

each proportion, by weight, of ammonia, at

least one proportion, by weight, of sulfur is separated. This however,is only possible when there is resent such a large excess of sulfuretedhyd rogen which will render the excess of sulfuraus acid harmless. Assuch regulation is diillcult, I prefer to add sulfur (or a sulfuryielding substancelto the liquor with which the gases, vapors orliquids, are treated, the sulfur being obtained either during theprocess, or from any other source; for instance, finely ground nativesulfur may be used. If there be an excess of sulfurous acid I may use,as the sulfur-yielding substance a sulfid or a polysulfid, (NHQ S forinstance, which will react with sulfurous acid in forming thiosulfate ofam- If there be no excess' of sulfurous acid, I may thionate (NH S,O forinstance, which will react with sulfureted hydrogen in formingthiosulfate and free sulfur. Even if there be less sulfureted hydrogenthan corresponds to the/am oniavonly thiosulfate of ammonia will beformed by the simultaneous reaction of ammonia, sulfurous acid .andvfree sulfur, or sulfur yielding substances.

- As an excess of sulfur does not affect the reactions, but ratherassists them, it is ad add a poly:

thiosulfate from sulfite and free sulfur, or

asulfur yielding substance, is however more readily effected in neutral,or basic liquors, than in acid liquors. By the conversion of the ammoniainto thionates loss of 'ammoma and sulfurous acld 1s avoided, am-

monium thiosulfate neutralizing any excess of sulfurous acid in formingammonium polythionates 2(NH )|S1Og+3SO:- (NH oiS10+ (NH4)QS400- Insteadof using free sulfurous acid, compounds may be used which, as is thecase the with acid sulfites, or olythionates, contain, or act like, freeacid under the action of hydogen sulfid, or of other sulfid. If there bemore sulfureted hydrogen than ammonia in the gas, I preferably add apolythionate, and if there be none or less sulfureted hydrogen thanammonia in the gas,

I preferably add an acid sulfite, but even then I may add a polythionate(which may 1 be either a dithionate, a trithionate, a tetra thionate, ora pentathionate.) A liquor is finally obtained which contains, besidesammonium thiosulfate and polythionates, the sulfur added in excess andeventually part of the sulfur, resulting from the mutual reaction ofsulfurous acid, or its substitutes, with sulfureted hydrogen or itssubstitutes. The sulfur may now be filtered off and, by

rocess hereinafter described, the ammonium thionates may then beconverted into sulfate, with the simultaneous separation of sulfur. Itis however preferable to first effect the conversion of the thiosulfatefirst into polythionate and then into sulfate, or directly into sulfate,and only then to filter off-.the sulfur separated by this process,

I may carr out my invention as described in the followlng severalexamples. But I do not, of course, limit myself to the particular waysdescribed hereafter, the ways to carry out the invention may vary,according to the conditions and proportions in which the substances tobe combined, will be present.

If coal gases, for instance, be subjected to the process and gaseoussulfurous acid, of any origin, and in any condition, as regardsconcentration, is to be used for treatment, the way' of this treatmentwill vary according to the proportiomof ammonia and sulfureted hydrogencontained in the coal gas.

Let it firstbe presumed, that the as contains only ammonia but nosulfurete hydrogen, I will then proceed as follows: Gaseous sulfurousacid, is introduced into the gasin such proportion as is equivalent to,or exceeds the amount of ammonia in the gas, and

this is simultaneously washed with water or with a liquor to whichsulfur is added. The amount of sulfur added must be at least equivalentto or exceed the-amount of ammonia in the gas. Instead of adding freesulfur, I may introduce into the gas or into the washing liquor a sulfuryielding substance, sulfureted hydrogen or any sulfid. If I addammonia-monosulfid for instance, such an amount must be added, that theproportion of ammonia in it is at least equivalent to, or exceeds thedouble by weightof the ammonia in the gas. I may also dISSOIVG Let itfurther be presumed, that the coal gas, besides ammonia containssulfureted hydro en. In this case on oneproportion by welght ofsulfureted hydrogen contained in the gas, the amount of the sulfurousacid introduced must be increased at least for one proportion by weight.Part of the sulfurous acid will then act upon sulfureted h drogen inyielding free'sulfur, which will combine with other part of sulfurousacid and with ammonia to form thiosulfate of ammonia. The amount ofsulfur, or a sulfur yielding substance to be added may therefore bediminished. But as the action of sulfurous acid on sulfureted hydrogenis a sloW one, there must be added so much sulfur, or a sulfur yieldingsubstance, that in any case sulfur is n excess and no sulfite is formed.

The sulfurous acid will be in a very diluted form, after being mixedwith the coal fga-s, therefore its absorption by the washing liquor willbe aslow one. Therefore, instead fof introducing sulfurous acid into thegas, I prefer to absorb it in water or in any salt solution, forinstance in an ammonia salt solution, and then to treat the gas withthis liquor. The proportions of sulfurous acid and of sulfur or sulfuryielding substance will be the same as above stated. I may also extractthe ammonia from the gas by washing it with water and then, with the am-'monia water thus obtained, treat gases, or

vapors, containing sulfurous acid, 'sulfur or a sulfur yieldingsubstance being added if and as far as required, the proportions beingthe same as above stated. If the ammonia water thus obtained, containsmonosulfid or1 'olysulfid of ammonia, the addition of su be diminishedaccordingly.

ur or a sulfur yielding substance may Instead of sulfurousacid gases Imay add to the washing liquor, or to the ammonia water, acid sulfites.'In this case the prothiosulfate,

portion of sulfur or sulfur yielding substance must be increasedaccording to the sull'ite added, in order to combine with this informing thiosulfate, whereas the sulfurous acid yielded from the acidsulfite acts like free sulfurous acid as above stated. As it isdifficult to add the gases or liquors in the rightproportlons,

I prefer to add in every case anexcess of sulfurous acid, or anacid-sultite, and of sulfur or a sulfur-yield ing substance. While thelatter will not be lost, in case of an excess of sult'urous acid, thisexcess will escape uncombined, if the gases and the washing liquor aresupplied to the washing apparatus in 0 posite direction. In this casethe gas is preferably subjected to a second washing process afterleaving the first water, the washing liquor used in the second water,containing ammonium or an alkali, or an earth-alkali, thiosulfate. Thethiosulfate will absorb the sulfurous acidcontained in the gas, or whichescaped from the first washing process, and ].)olythionate will befOIIllQt. If, however, the gas and Washing liquor be supplied to thewashing apparatus in the same 'direction, the thiosulfate, formed by thereaction between the ammonia sulfur, sulfurous acid, and occasionallysulfureted hydrogen, will, in tbefurther course of the washing process,absorb the excess of sulfurous acid, polythionates being thereby formed.The gas and liquor will react as aforesaid, whether they be cold or hot.The temperature depends upon the tempera-lure of the gases to betreated. If it be desired to further concentrate with ammonia salt theliquor leaving the washing apparatus,,the liquor is again treated withsulfurous acid, polythionate being formed from the thiosulfate and theliquor-becoming acid, with free sulfurous acid, and then this solutionis again passed through the washing apparatus. from time to time, addedto the liquor according to requirements. If the gas containsconsiderably more sulfureted hydrogen than corresponds to the ammonia,no further addition of sulfur is needed during the second passage, orrepeated passages, of the liquor through the washing apparatus, but itisnecessary that a sufficient amount of free sulfur, or of present inthe lye.

By the alternating treatment of the liquor Sulfur is,

with the goal gas containing ammonia and with siilfurous acid, theliquor gradually absorbs such an amount of ammonia that it can beadvantageously used for the manufacture of crystallized ammoniumsulfate. For this purpose I proceed as follows: The

liquor is treated with sulfurous acid of any concentration, temperature,or origin (air being added if required), and heated at the same time, orsubsequently. By this treatment the thiosulfate present is in the firstpolythionate, shall be instance oxidized, and converted intopolythionate. This treatment with sulfurous acid is continued(preferably at from 40 to centigrade) until most of the thiosulfate hasbeen oxidized to polythionate. Thereuponthe liquor is more stronglheated, preferably up to boiling point, w ereby the polythionates aredecomposed into free sulfur and sulfate, sulfurous acid being evolved.It is not necessary, in thislatter stage of the process, to introducemore sulfurous acid, but a further supply thereof will do no harm.

The sulfurous acid not absorbed in the oxidation process, as well asthat evolved by the decomposition of the polythionate into sulfate canbe used for the washing operation. After the oxidation of the liquor iscompleted, the sulfur is separated from the ammonium sulfate solution ina centrifugal apparatus, or filter press, or by decantation, or bysimple draining, and, after being washed, it is used as hereinbeforestated partly as such, and partly in the form of sulfurous acid, and anyexcess of sulfur yielded may be utilized for other purposes. The puresolution of ammonium sulfate, which can be so readily enriched in thegas washing operation that it finally contains 40 per cent. or more ofammonium sulfate, is evaporated in 'vacuo, or in an open vessel, untilit crystallizes and the ammonium. sulfate is separated (which can bedone in the usual manner) from the mother liquor.

Instead of sulfurous acid, I may use such salts of ammonia, an alkali,or an alkali earth, as will (as is the case with sulfite s. orpolythionatc's), on being acted upon by sulfureted hydrogen, or anyother sulfid, exercise an oxidizing influence on hydrogen sulfid, withformation of thiosulfate and free sulfur. I

The action of ammonium polythionate, for instance, is-for the bettercomprehension of my invention illustrated by the fol-' lowing example:Let' it be presumed that ammonia from gases, or vapors, which, besidesammonia, also contain hydrogen sulfid, is to be combined. In this case,if the hydrogen sulfid present be equal to, or in excess of, the ammoniapresent, the process is as follows: Coal gas for instance is treatedwith an acid, neutral or basic, liquor which contains ammoniumpolythionate. Sulfureted hydrogen, as well as ammonium sulfid, containedin the gas, exercise a reducing action on the polythionate, sulfur beingthereby separated. In the first-case for instance by the action ofsulfureted hydrogen,- ammonium thiosulfate and free sulfur are formed.In the second case, two molecular proportions of ammonium thiosulfateare directly produced by theaction of one molecular proportion ofammonium sulfid on one molecular proporpresent, a pol thionate solutionwhich contains free sul ur, or free sulfurous acid, or both, may beused, or, during the process of the combination of the ammonia,sulfurous acid' in gaseous form may be supplied, sulfur, orsulfur-yielding substance, being added in both cases if required. Theliquor obtained in this process, containing malnly ammonium thiosulfate,is then treated with sulfurous'acid until the main part, or all,

of the thiosulfate is converted into polythionate and this liquor maythen again be used I for treating the coal gas.

The alternate treatment ofthe liquor with the coal gas, and withsulfurous acid, is

repeated until the liquor contains the desired amount of ammoniathionates. Thereu on the liquor is subjected to the hereinbe oreescribed oxidizing process to convert the '"ammonium thionates intosulfate yielding thereby free sulfur and sulfurous acid. Should the gascontain only sulfureted hydrogen and noammonia the alternate treatment.of the polythionate solution with gas and sulfurous acid is the same asaforesaid. The sulfur precipitated by this treatment is from time totime filtered off from the liquor.

In allcases be-it with gas containing ammonia'and sulfureted hydrogen oreither, it is preferable to use such an excess of 'olythionate solution,that in the solution ieaving the'washing apparatus the polythionate isnot completely reduced into thiosulfate, in order to have all thesulfureted hydrogen and ammonia absorbed.

The accompanying drawing re resents diagrammatically apparatus suita lefor' use in carrying out this invention, but I do not, ofcourse, limitmyself to this par ticular way and apparatus,

A is a gas washer and B is an absorption.

tower, C is a tank from which liquor is su plied to the washer A by apump D.

E. is a centrifugal machine. Fis a vessel hereinafter called a boiler. Gis an air compressor and N is a sulfur oven.

I will presume that the apparatus is to be used for treatment of coalgas,.which contains ammonia together with an excess of sulfuretedhydrogen, which are to be extracted. The coal gas enters the washer A ata and is therein treated by the liquor, containing, forexample, ammoniumpolythionate. If the gas is cold, the li uor or the gas, or both may beheatedbe ore, or during their passage through the washer A, in order toaccelerate the absorption of the sulfureted hydrogen by thepolythionate. By the action of this liquor, the ammonia and sulfuretedhydrogen are absorbed, pol thionate being reduced to thiosulfate ansulfur being precipitated. The purified gas leaves at a. The liquor isconstantly pumped up, by the pump D, through the ipes e, e?,' and intothe washer A. The iquor, when it leaves the washer A, contams mainlythiosulfate of ammonia and free sulfur, it enters the absorption towerby the pipe a and, while it runs through I the said tower, air,containing sulfur dIlOXld, is blown through the said tower, the said airand sulfur dioxid entering at b. The liquor absorbs sulfur dioxid andthe ammonium thiosulfate is converted into polythionates.

The liquor may be slightly heated-before or during its passage throughthe tower B in order to accelerate] the formation of .the polythionates.This'regenerated liquor leaves the tower B by the pipe bfand enters thetank- 0 from which it is again pumped by the pump D into the washer A.By thus constantly circulating through the washer A, and the absorptiontower B, the liquor accumulates ammonia thionates.

As soon as the liquor has attained a certain strength part of it ispumped by pipes e and e to the boiler F in which the liquor is treatedwith sulfur dioxid in the cold, or at an elevated temperature, untilall, or nearly all, of the'thiosulfate is converted into polythionates.Then the liquor is decomposed by stronger heating or by boiling, sulfateof ammonia being formed, sulfur being precipitated, and sulfur dioxidbeing given 013:. The sulfur dioxid is led by. the pipe I) to theabsorption tower B. After the formation of the sulfate of ammonia iscomplete, the liquor, containing the sulfur precipitated, is.

discharged by the valve f into the centrifugal machine E in which thesulfate of ammonia solution is separated from the sulfur.

The sulfur may be burned in the sulfur oven N. For this purpose air-isblown through the pipe g into the said oven'N by the air compressor G.The gases comin from the oven N (which ga'ses contain sul dioxid,

, together with excessof air) enter the tower 'B by the pipe b, or theboiler F by the pipe I), and the waste gases, after having given offtheir sulfur dioxid to the thiosulfate li uor running through the tower-B, leave v this apparatus bythe pipe '6.

clalms the ex ression eted hydrogen ,whe re or sulfureted hydrogen, orboth, and thereference to matters in which they are contained includesgases, vapors, or liquids, containing ammonia or sulfureted hydrogen, orboth, and the mention of the use of-sulfuro'us acid includes also theuse of substances ca pable of yielding sulfurous acid, or of beingusedin place of sulfurous acid, and the mention of sulfur includes also theuse of substances capable of yielding sulfur and the expression saltsmeans salts of ammonia, alkali, or earth alkali.

I claim as my invention I 1. In'the'absorption, by meansof sulfurousacid, of ammonia and sulfureted hydrogen, from matters containing them,the step of treating such matters with the sulfurous acid in thepresence of as much sulfur as. is necessary to convert the ammoniacombined with the sulfurous acid into thiosulfate, then converting thethiosulfale into polythionates by further treatment with sulfurous acidand decomposing these polythionates by heat into sulfate of ammonia andfree sulfur, as hereinbefore explained.

2. In the absorption of ammonia and sulfureted hydrogen, from matterscontaining them, the step of treating a liquor containing saltsalternately with sulfur dioxid and with the matters containing ammoniaand ,sulfureted hydrogen in the presence of sulfur, as hereinbeforeexplained. l

3. In the absorption of ammonia and sulfureted hydrogen from matterscontaining them and in which the ammonia' is present' with an excess ofthe sulfureted hydrogen,

the treatment thereof with sulfurous -acid, said acid, ammonia andsulfureted hydrogen being so proportioned that, in consequence of therecuperation of sulfur, no ammonium sulfite, but only ammonium thionateis duced, as hereinbefore ex lained.

4, In the absorption 0 ammonia and sulprofureted hydrogen from matterscontaining fureted hydrogen from matters containing them, the step oftreating alternately a solution of polythionates with the matterscontaining ammonia and sulfureted hydrogen" and with sulfur dioxid, ashereinbefore explained.

6. In the absorption of ammonia-and sulfureted hydrogen, from matterscontaining them, in which ammonia preponderates, the step of treatingsaid matters alternately with a solution. of polythionates to whichsulfur has been added, and with sulfur dioxid, as hereinbeforeexplained.

7. In the absorption of ammonia and sulfureted hydrogen from matterscontaining them, the step of treating a solution of ammonium thionatewith sulfurous acid at a temperature below boiling point so as toconvert .the thiosulfate present into polythionates and then oxidizingthe polyt-hionates to sulfates by heating the solution to about, orabove, the boiling point, as hereinbefore explained. v

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

WALTHER FELD.

Witnesses:

HENRY HASPER WOLDEMAR HAUPT.

